Jason Kubel prior to the game against the San Diego Padres. IMAGE: Christopher Hanewinckel-USA TODAY Sports

It’s no secret that the Diamondbacks are struggling to score runs. Some of that can be chalked up to their inability to hit with runners in scoring position, but there’s also another culprit: they’re struggling mightily against left-handed pitching.

With Jason Kubel, Gerardo Parra, Didi Gregorius, Miguel Montero, Eric Chavez and Eric Hinske all being left-handed batters, teams have been able to neutralize the Diamondbacks when they put a lefty-starter on the mound. With Adam Eaton set to arrive in Phoenix in the near future and AJ Pollock likely headed back to AAA, that will add another left-handed hitter to the lineup at the cost of a right-handed one.

Against righties, the Diamondbacks rank ninth in the majors with a .754 OPS. Against lefties, they rank 24^th with a .669 OPS. These splits are problematic and will continue to be so unless the team can make some adjustments. Currently, Kubel (.452), Chavez (.333), Hinske (.600), Montero (.657) and Parra (.658) are all struggling against lefties, showing typical platoon splits. Chavez and Hinske are primarily bench bats that face right-handed pitching late in games, but Kubel, Montero and Parra are expected to drive the offense. Gregorius has hit lefties well in his short time with Arizona, but showed some splits in the minors.

The biggest problem lies in the fact that the team doesn’t have a right-handed compliment to Jason Kubel. His only real value to the team is with his bat since his defense rates so poorly. When lefties take the mound, Kubel is effectively neutralized. Adding Adam Eaton into the lineup may soon be able to fix that defensive issue, but it likely won’t help much in terms of offense against left-handed pitching.

Look for the team to perhaps make a move in the near future to acquire a right-handed outfielder or bench bat with power that they feel more comfortable with than Pollock. Eric Hinske isn’t being used much and could be flipped or the team could put together a package around Pollock to obtain a player more to their liking. Selling high on Pollock might be a good idea and while he’s certainly a functional player, he may not be what the organization needs right now.

This team is in a win-now position and may need to do something to remedy this problem sooner rather than later. Triple-slaching .224/.303/.335 against lefties isn’t going to get it done down the line. With starting pitchers like Clayton Kershaw, Madison Bumgarner, Barry Zito, Hyun-Jin Ryu and others likely playing critical roles against the Diamondbacks down the stretch, a strong lineup against lefties is going to be critical. The Dodgers won’t stay in last place forever and the Giants aren’t going anywhere, so improvements must be made. While sample size and slow starts can account for some of the issues, a roster change may be the best solution.

The four outfielders destined to make the Opening Day roster were Cody Ross, Jason Kubel, Adam Eaton and Gerardo Parra. An injury to Ross kept him out for the first 10 games and just when he was ready to return, Kubel went down and has been out for the last 13 games and counting. Eaton hasn’t played at all and is likely still out for two or three more weeks with an elbow strain. In case you aren’t counting along, that leaves Gerardo Parra as the only constant in this equation.

Diamondbacks center fielder Gerardo Parra scores on a single by center fielder A.J. Pollock in San Francisco. Image: Ed Szczepanski

And what a constant he’s been. Through 22 games, he’s hitting .315/.374/.461 primarily from the leadoff spot while continuing to play outstanding outfield defense. His OBP is jumpstarting the offense and he’s scored 15 runs already. Of his 28 hits, he’s racked up eight doubles, a triple and a homer, making good use of his gap power. He’s been the team’s most valuable position player thus far and it’s safe to say that they wouldn’t be battling for first in the division without him.

So what happens when Adam Eaton returns?

We have to assume that Ross will stay in right and Kubel will resume his duties in left when he’s healthy. That leaves centerfield as the only open slot on a regular basis. We’ve seen that Parra can definitely get the job done, but Eaton was supposed to be the new centerfield star before his injury. Assuming that Alfredo Marte and AJ Pollock both head back to the minors once everyone’s healthy, who goes to the bench, Eaton or Parra?

While Parra has been the super-sub the last few years, he’s 26 and hitting his prime. I’m not sure the team can afford to take his bat out of the lineup. Eaton was essentially promised a starting job, but Parra very well may have stolen it from him. Perhaps Eaton becomes the defensive substitute late in games, moving Kubel to the bench and Parra to left when the team has a lead late in games. And given the frail nature of Kubel and Ross, both of whom have missed their share of games to the DL over their careers and aren’t getting any younger, there will likely be starts to pick up along the way for whoever assumes the super-sub role.

We have a few more weeks to monitor this situation, but it’s looming on the horizon and might be the most important roster decision made by that point in time. Unless Parra plays his way out of the lineup between now and then, I can’t imagine Gibby yanking him from the lineup and putting him on the bench in favor of a guy who hasn’t played a regular season game this year. Maybe it’s just me, but Parra is likely the best option for the team in center given what he’s done to date, even when Eaton returns.

Maybe Parra will hit a slump. Maybe Eaton begins the year by hitting .350 when he makes it into the lineup and never looks back. Who knows what the future holds? All we know is what we’ve seen thus far, and thus far, Gerardo Parra has shown that he deserves to be a starter.

*Stats accessed 4/26 via FanGraphs

Image: Matt Kartozian-USA TODAY Sports

Spring isn’t all sunshine when it comes to battling for a spot on a 25-man roster for players, either.

The D’backs starting lineup is pretty much set heading into 2013 meaning the battles will be in the back end of the rotation, the bullpen and on the bench.

Miguel Montero, Paul Goldschmidt, Aaron Hill, Martin Prado, Chad Pennington, Gerardo Parra, Jason Kubel, Adam Eaton, Cody Ross and Willie Bloomquist are locks along with Ian Kennedy, Trevor Cahill, Brandon McCarthy and Wade Miley in the rotation. In the bullpen, JJ Putz, Heath Bell, David Hernandez and Brad Ziegler are also pretty much assured spots.

With the D’backs likely to carry 12 pitchers that leaves one starter, three reliever spots and three bench spots open.

Starting spot battle: Tyler Skaggs vs. Randall Delgado

Delgado was acquired in the Justin Upton trade along with Martin Prado. Delgado is probably projected for a back-end starter for his career and has solid stretches throughout his career so far. He owns a career 3.95 ERA over 127.2 innings in the majors. Skaggs has been a top-tier pitching prospect for a few years and appears to be ready to pitch a full season in the bigs. Skaggs owns a career 2.98 minor-league ERA. He did struggle a bit in his brief appearance with the D’backs last season with a 5.83 ERA over 29.1 innings.

Edge: Skaggs

Three bullpen spots: Patrick Corbin vs. Tony Sipp vs. Matt Reynolds vs. Josh Collmenter

Sipp and Reynolds have each spent quality time in the majors with solid results. Sipp has thrown 220.1 innings over the past four seasons with a 3.68 ERA and Reynolds has thrown 126 innings over the past three seasons with a 3.93 ERA. Reynolds and Sipp, both lefties, are solid bets to make the bullpen.

That leaves the final spot for Corbin and Collmenter to battle it out. Corbin is also a leftie and was effective over long stretches in the beginning of last season but then struggled down the stretch. Collmenter on the other hand, struggled mightily early and then picked it up as the season progressed. Edge: Collmenter

Bench Spots:

Back up catcher – Wil Nieves vs. Rod Barajas

Nieves was productive in limited time with both the D’backs and Rockies last season, hitting .301/.330/.410 over 89 plate appearances. On the other hand, Barajas was pretty awful in 321 plate appearances for the Pirates in 2012. He hit .206/.283/.343 for the season.

Edge: Nieves

With an outfielder and a utility player in Bloomquist on the bench already, the D’backs have some flexibility in the two remaining bench spots: Eric Chavez vs. John McDonald vs. Tony Campana vs. A.J. Pollock vs. Matthew Davidson

Edge: Chavez and McDonald